The diffuse infiltrating lymphocytosis syndrome (DILS) may be the most common rheumatic disease seen in HIV+ individuals. The presence of DILS may retard the the progression of HIV infection. The aims of this study are to 1) determine the prevalence of DILS in a large HIV+ population, 2) better define the natural history of DILS by long-term followup, 3) by studies of HLA and other genetic markers better define those at risk for DILS and to determine the effect of the markers on DILS, 4) examine the response to corticosteroids in treating DILS. Since the study began in July, 1995, 102 patients meeting criteria for DILS have been enrolled. The association with HLA-DR.Bl alleles encoding the I..DE epitope in the third diversity region of the HLA-DRBI outermost domain is again seen in African Americans (and marginally so in Caucasians) though no association in Hispanics is seen. The prevalence of DILS at the Thomas Street clinic in Houston, established in a survey of 522 individuals by physicians trained to look for parotid enlargement, is between 2.9 and 3.4% (maximum and minimum).